How To Test The Throttle Position Sensor (1997-2004 4.6L, 5.4L Ford F150, F250)

Testing and troubleshooting the throttle position sensor (TPS) on your Ford or Lincoln car, pick up or SUV is an easy thing to do. You don't even need a scan tool to test it. A simple multimeter will suffice and in this tutorial, I'll take you thru' the whole diagnostic process step by step.

OK, one last thing before we jump into the testing process, you can find a complete list of 4.6L and 5.4L Ford F150/F250 'how to test' tutorials and wiring diagrams here: 4.6L, 5.4L Ford F150, F250, And F350 Index of Articles.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (Ford 4.6L, 5.4L) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 4.6L V8 Ford F150, F250: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004.
• 5.4L V8 Ford F150, F250: 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004.

Quite a few other vehicles use the same TP sensor as the F-Series pickups listed above and are tested in the same way. Take a look at the "Applies To" box (left column on desktop devices - bottom of page on mobile devices) to see the application list.

E-SERIES VANS: The TP sensor diagnostic tests can be found here:

• How To Test The Throttle Position Sensor (1997-2003 4.6L, 5.4L V8 Ford E150, E250, E350) (at: troubleshootmyvehicle.com.

CROWN VICTORIA/GRAND MARQUIS: The TP sensor diagnostic tests can be found here:

• How To Test The Throttle Position Sensor (1995-2004 4.6L Crown Victoria, Grand Marquis) (at: troubleshootmyvehicle.com.

Symptoms Of A Bad Ford TPS

The most common symptom is the check engine light (CEL) is on (also known as the MIL=Malfunction Indicator Light) on your instrument cluster and annoying the heck out of you as you drive. Among other things, your vehicle might be experiencing:

1. TPS diagnostic trouble codes (DTCs) stored in the vehicle's computer's memory.
   • P0121: Throttle Position (TP) Circuit Performance Problem.
   • P0122: Throttle Position (TP) Circuit Low Input.
   • P0123: Throttle Position (TP) Circuit High Input.
2. Really bad gas mileage.
3. Transmission does not shift out of second gear.
4. No power as you accelerate the vehicle.
5. Hesitation when you step on the accelerator pedal.

What Tools Do I Need?

As mentioned at the opening of this article, all that you'll need to be able to use the info and perform the tests in this article is a multimeter (don't have a digital multimeter? Need to buy one? Click here to see my recommendations: Buying A Digital Multimeter For Automotive Diagnostic Testing).

You may need a helper to perform some of these tests.

Circuit Descriptions Of The Throttle Position Sensor

As you already may know, the throttle position sensor (TPS) on your Ford (or Mercury or Lincoln) vehicle has three wires coming out of its connector. Below are short descriptions of the signal each one carries. These are the circuit descriptions that we'll be using thru' out the rest of the article to test the TPS on your vehicle.

• Circuit labeled 1:
  • 5 Volts from PCM.
• Circuit labeled 2:
  • Throttle Position (TP) Signal Circuit.
• Circuit labeled 3:
  • Sensor Return (Ground) Circuit.

I recommend that when you test for the particular signal in the wire, that you use a tool to pierce the wire, such as a wire-piercing probe (click here so that you can see what one looks like: Wire Piercing Probe). Disconnecting and probing the front of the female terminal of the connector can get you into a lot of trouble, if you open up the terminal with the probe you're using.

One last observation, these three circuits go directly to the PCM. So you need to be careful not to short these wires to power (12 Volts) or you may fry the PCM.

How Does The Ford TPS Work?

Here's some very basic working theory that'll help you to understand the 'why' and 'how' of the three tests you're gonna' do with the help of this article. OK, in a nutshell, when you crank and start your Ford vehicle:

1. The PCM (Powertrain Control Module=Fuel Injection Computer) feeds the throttle position sensor with 5 Volts and a Ground.
2. This Ground is known as the Sensor Return in Ford tech speak.
3. As you step on the accelerator pedal, the TP sensor translates the amount of throttle plate opening (caused by the accelerator cable) into a voltage signal the PCM can use.
4. The PCM uses this voltage signal , that will vary with the amount the throttle opens as you accelerate or decelerate the vehicle, to inject fuel, control ignition timing, and the rest of the song and dance the computer has to do to get your vehicle moving or slowing down.

Pretty simple stuff, no? Well testing it is just as simple. Since you'll be working in the engine compartment, no need to tell you (but I'm gonna' tell you anyway) to be alert and be very careful. Use common sense and take all necessary safety precautions. OK, on with the show, go to: TPS TEST 1: Testing The TPS Signal.

Where To Buy The Throttle Position Sensor And Save

The following links will help you comparison shop for the factory original Motorcraft and after-market throttle position sensor (TPS):

Not sure if the TP sensors above fit your particular Ford vehicle? Don't worry, once you get to the site, they'll make sure they fit and if they don't, they'll find you the right ones.

TPS TEST 1: Testing The TPS Signal

To get our TPS sensor diagnostic started, we're gonna check its output voltage signal with a multimeter.

If the TPS is working correctly, its voltage output should increase as you open the throttle plate and decrease as you close it.

You'll need someone to help you in this part to lightly tap on the throttle position sensor's body with a screw driver (or other appropriate tool) as you observe your multimeter and actuate the throttle.

IMPORTANT: The throttle position sensor must be connected to its electrical connector for this test. You'll need to use a back probe on the connector or a wire piercing probe on the wire to see the voltage signal. You can see an example of this tool and where to buy it here: Wire Piercing Probe.

OK, let's start testing:

STEP 1:

1. 1

   Put your multimeter in Volts DC mode.

2. 2

   With the red multimeter test lead, and an appropriate tool, probe the circuit labeled with the number 2 (see the photo above).

3. 3

   Connect the black multimeter test lead directly on the battery negative (-) terminal.

4. 4

   Turn the key to its ON position but do not start the engine.

5. 5

   Your multimeter should read about 0.9 to 1 Volt (the reading on your vehicle will vary just a little, about ± 1 volt).

STEP 2:

1. 6

   Rotate the throttle plate by hand as you observe the multimeter.

2. 7

   The multimeter's initial reading should increase smoothly as you open the throttle plate to its Wide Open Position.

3. 8

   Now, slowly release the throttle plate to its fully closed position, all the while observing the multimeter's reading.

4. 9

   The multimeter's voltage reading should decrease in a smooth and linear fashion.

STEP 3:

1. 10

   Have your assistant tap on the throttle position sensor lightly with the butt of a screw-driver's handle as you open and close the throttle plate.

2. 11

   The TPS signal voltage should not be affected by the tapping.
   
   If the TP sensor is bad, the tapping will cause gaps in the voltage readings.

Let's interpret your test results:

CASE 1: The multimeter registered a smooth increase or decrease in voltage. This test result lets you know the TP sensor is working OK and is not the cause of the TPS fault code issue.

If a TPS diagnostic trouble code keeps illuminating the check engine light, see this section: TPS Code Won't Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The multimeter DID NOT register a smooth increase or decrease in voltage. This test result usually lets you know the throttle position sensor (TPS) is bad, but to be sure, we need to make sure that the TP sensor is getting power and Ground.

For the next test, go to: TPS TEST 2: Testing The 5 Volt Reference Signal.